CH642798A5 - Reproduction device of a video signal. - Google Patents

Description

642 798 2

CLAIMS a relatively high frequency domain and thereby

1. Device for reproducing recorded video signals which said delay means further comprise in successive parallel tracks making an angle with the frequency conversion means (27,31) connected before the longitudinal direction of a recording tape, com- and after said first and second respec-taking delay lines: 5 tively to transpose the frequency of the two main reproduction video signals (1 A, 1B) diametrically produced in said high frequency range before the opposite ones and having different steering angles; delaying in said delay lines and in order to recover said at least one auxiliary reproduction head (2A) having video signals delayed in their frequency range by the same angle of direction as that of one (1 A) of said signals.

main reproduction, said reproduction head 7. Device according to claim 6, characterized by the auxiliary fact being angularly offset by (n -I- 0.25) H '(n: 0 or that said frequency conversion means comprise a positive integer, H ′: angle corresponding to a hori period (an oscillator (23) producing a carrier signal for said zontals on the band) relative to the other (1B) of said frequency conversion means heads and a first and a second main reproduction; phase shifter (32,33) through which said signal carries

head control means (6,8,10; 26,30,34,35) 15 tor is supplied to said frequency conversion means for reproducing the video signals of said main heads after the first and second line of delay, res-

blades and auxiliaries so as to reproduce said signals visually during the reproduction of the first and second deo using said main reproduction heads (1 A, type of recording.

1B) when the tape is transported longitudinally to an 8. Device according to claim 2, characterized by the fact standard speed and for reproducing said video signals to that said delay means further comprises using one of said heads main reproduction (1 A) means (42,43,44) for inserting a synchronization signal and said auxiliary reproduction head (2A) when the reference vertical in the video signal delayed by said bands is stopped; and means of delay.

delay means (3,4; 24,25) for alternately delivering the reproduced video signal and said reproduced video signal 25

when the tape is stopped, said delay means impar-

The present invention relates to a device for reproducing said video signal reproduced when the tape is at the rear.

stop a delay corresponding to the jump which appears in synchronization of video signals recorded in parallel tracks nism with the switching between said successive reproduction head making an angle with respect to the longitudinal direction

main (1 A), and the auxiliary reproduction head (2A). 30 dinal of a recording tape.

2. Device according to claim 1, characterized in that the invention seeks more particularly to prevent it from reproducing a first type of recording in which oblique distortion when the reproduction is carried out with the horizontal synchronization pulses recorded on the magnetic tape or other recording means to in neighboring tracks are offset from one another in the direction of the stop.

tion of said tracks and a second type of recording in a conventional video tape recorder (VTR),

which the horizontal synchronization pulses of the tracks is provided two transducers or heads with slits orient-

neighbors are aligned with each other and by the fact that said tees at different lateral angles for recording and repro-

delay means comprises a first delay line which draws signals into respectively adjacent tracks for delaying the video signals during the reproduction of the pre- or alternating, in order to reduce crosstalk while at the same time

mier type of recording and a second delay line, 40 putting an increase in the recording density,

producing a delay different from that of the first line of This is relatively easy to execute since a device for delay, during the reproduction of the second type of record- record and / or magnetically reproduce visual signals.

very much. deo of two transducers or heads operating alternately-

3. Device according to claim 2, characterized by the fact, arranged in a diametrically opposite manner and hen offset of the horizontal synchronization pulses 45 before having slots with different direction angles, in the neighboring tracks has a value of (n + 0.75) Th (n: 0 or The magnetic strip is wound in a helix around a positive integer, Th: distance on the track corresponding to a tie of the perimeter of the guide drum and it is moved longitu-period horizontal) and by the fact that said first line of direction during the rotation of the transducers or heads, this delay (24) produces a delay of H and that the second line of which allows them to explore respective tracks on delay ( 25) produces a delay of '/ 4 H (H: horizontal period). 50 tape to record or reproduce signals. In the o

4. Device according to claim 3, characterized by the fact of recording such a VTR (tape recorder that said delay means further comprises a pre-video) with helical exploration, each head produces the magnet- mier switching circuit (26) for switching said pre- tion of magnetic domains in the magnetic magnetic coating and said second delay line in response to the repro- of the band in which would appear, if such domains duction of said first and said second recording type 55 were visible, a series of parallel lines or bands and a second switching circuit (35) for delivering selectively each having a length equal to the width of the track and vely the reproduced video signals and the video signals retar- an orientation corresponding to the direction angle of the dice of the first or the second delay line. slot of the respective transducer or head. In the operation

5. Device according to claim 4, characterized by the fact of reproduction or reading of the device, each track is that said delay means comprise means of 60 explored by the transducer or the head whose slot is orient-control (40) switch for switching said second tee along the parallel but fictitious lines of this track, switching circuit (35) at each frame interval when the slot of the transducer or the head exploring one of the reproduction of the second type of recording and shading to reproduce the video signals recorded on that two-frame interval when playing the pre-track makes an angle with respect to the aforementioned fictitious lines-type recording. 65 born from tracks adjacent to the track explored. Because of this

6. Device according to claim 2, characterized by the above fact, if a transducer or a head, during the exploration that the first and the second delay line have a character of a track for reproducing the signals frequency-rich video that promotes the passage of recorded signals, partially overlaps an adjacent track or

3,642,798

also produces the signals recorded in the latter, To eliminate the oblique distortion of the image produced, the well-known loss of direction angle produces an attenua- has already been proposed by the same applicant to use a new tion of the crosstalk signal reproduced from the ad-circuit track described in the patent application US 78,774 filed the underlying. September 25, 1979. According to this request, the video signals

Furthermore, it is common practice to record if products are delayed by a value corresponding to the decimal point.

video signals with the so-called H alignment in order to prevent delays between the horizontal synchronization pulses

interference or crosstalk due to synchronized signals on neighboring tracks and, when operating at

sation and erasure horizontal contained in the signals different reproduction speeds, a switching circuit

video recorded in successive parallel tracks. In tion alternately delivers video signals such as repro-

the recording of H-aligned video signals, the output by the head and the delayed reproduced video signals, the state hoppers of the margins between the regions in which of the switching circuit being changed each time the valles of lines are recorded in each track are ali- reproduction head passes from one track to another neighboring track gnnes (in the direction transverse to the direction longitudi- in its movement along the exploration path.

There are also known another type of TRV including at the successive regions in which the line intervals 15 minus two main rotating heads with angles of di-

are recorded in the adjacent tracks. different rection and an auxiliary rotating head having the

If, during the reproduction operation, a VTR with the same angle of direction as that of one of the rotating heads

helical exploration type, the speed and direction of the main motes and arranged to explore substantial-

The edge of the tape are respectively equal to the speed and the same track as this main head. In the case of standard tape direction during recording, the slow motion reproduction of the recorded video signals, the scanning path of each head or turn-tape transducer is driven intermittently at a rate of a nant can be brought to coincide with that of a frame track at each time interval corresponding to the respective recording rate in order to reproduce properly the desired deceleration and, during the stopping of the tape, the si -

video signals from this track and the above described video signals are alternately reproduced by one of the

allow substantial elimination of crosstalk due to the main rotating head and the auxiliary rotating head, then the signals recorded in the tracks adjacent to which the video signals are alternately reproduced by the is explored. two main rotating heads when the belt is moving

In general, in the embodiments practically.

As for VTRs of the helical exploration type, the standard speed When the above delay circuit is used with the tape dart during recording is chosen from the new type of VTR described above, this delay circuit de-niere adequate in relation to the magnitude of the diameter of the just complicated execution and it is difficult to control it, tambourguide, so that the video signals are recorded From the above, the purpose of the present invention very with the alignment H in the closest to the other tracks is to provide a device for reproducing video signals recorded by the same head. However, it is sometimes necessary not to present the difficulties mentioned above in connection with the fact that, during recording, the magnetic tape is worn with the existing devices. More particularly, the object moved at different speeds, other than the jet tape speed of the present invention, is to provide a restandard device, to increase the recording density of the video signal production of relatively simple design. general video. It is then no longer possible to produce a pie device to prevent the oblique distortion of a repro-image in which the video signals are recorded with the aligned line when the reproduction operation is executed with H, if the Tape must be advanced two or more at 40 speed and / or direction of the tape different from that of different tesses. For example, if video signals are re-used by recording.

registered with the alignment H when the strip is driven or To achieve this goal, the devices according to the invention include

transported longitudinally at a predetermined speed, takes two main reproducing heads diametrically the signals are not recorded with the alignment H when opposite and having different direction angles, at least that the tape is moved at half the predetermined speed - 45 an auxiliary reproduction head having the same angle of termination. direction as that of one of said reproduction heads

If the speed of the tape during reproduction is sub-main, said auxiliary reproduction head being offset so different from the speed during recording, angularly by (n + 0.25) H '(n: 0 or integer positive, H ': angle or if the direction of movement of the tape during the re-corresponding to a horizontal period on the tape) by production is different from the direction when recording- 50 compared to the other of said heads of main reproduction, ment, the exploration path of each head can make a year of the head control means for the reproduction of the acronyms large enough with the direction of the recorded tracks, video signals of said main and auxiliary heads so that '' by traversing such exploration paths, cha- to reproduce said video signals using said re-head heads that advance and reproduce the video signals of the first main production when the tape is transported as gi-track, then those of one of the other neighboring tracks in which 55 tudinally at a standard speed and for reproducing said positions of the horizontal synchronization pulses video signals using one of said recorded reproduction heads are offset, for example, of> / 2 period of main ba- and of said auxiliary reproduction head when horizontal layout (H). If such signals reproduced first on the tape are stopped and delay means to deliver from the first track and then from another track the video signal reproduced and said video signal repending a frame interval, and that they are demodulated and in-60 produced when the tape is stopped, said delay means seen at a television receiver, there is a disruptive-imparting to said video signal reproduced when the tape tion due to the jump of 112 H in the continuity of the pulses of is stopped, a delay corresponding to the jump which appears in horizontal synchronization when jumping from one track to the other synchronism with the switching between said reprode head the head or of the reproduction transducer. During main production and the auxiliary breeding head.

Scan period in which the automatic control circuit 65 Other features and advantages of the present invention

tick of the frequency (AFC) of the television receiver ab- tion will appear in the following description, made as sorbe the jump of lji H an oblique distortion appears in the example i, and using the drawing in which the same referen-

mage reproduced. these denote the same elements.

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The flg. 1 is a plan view showing a known arrangement the periods or periods of the video signal are recorded. It is visible with a rotating head in which the heads are arranged with one that in the case where the positions corresponding to the start of the respective angular distance of 180 °, the recording in the adjacent tracks Ai and Bi are offset fig. 2 and 3 are diagrams showing models linked with respect to each other from a distance of 3/4 H in the recording respectively with and without alignment H and 5 direction of the tracks, the positions at which the recording used for the explanation of the jump of the synchronization signals - starts in the neighboring tracks recorded by the same horizontal tion during a reproduction mode with fixed head image, for example the tracks A1 and A2 recorded by the head 1A or stopped , or tracks B1 and B2 recorded by leitete 2A are offset in fig. 4 is a block diagram of a known circuit for correcting one with respect to the other by a distance of 1 '/ 1H in the jump section, 10 rection of the tracks. Due to the above and as indila fig. 5 is a timing diagram used to explain that in fig. 2B, the positions at which the pulses or if the operation of the circuit of FIG. 4, general horizontal synchronization of video signals are fig. 6 is a plan view showing an example of a recorded in each track Ai are offset by xji H in the rotary head assembly according to the invention, direction of the tracks from the positions at which the pulses

fig. 7 and 8 are diagrams showing models 15 horizontal synchronization sions are recorded in recording respectively with or without H alignment and the closest track Ai, i.e. the recorded track used for the explanation of the skip synchronization signals immediately before or the immediately recorded track horizontal tion during a still image reproduction mode, after by the same head. Similarly the positions in fig. 9 is a block diagram showing an example of the circuit in which the horizontal synchronization pulses are fired with jump correction according to the invention, recorded in each track Bi are offset by! / 2 H by FIGS. 10 and 11 are diagrams of the times used in relation to the positions at which the synchronization pulses

to explain the operation of the circuit in fig. 9 and horizontal position are recorded in the quickest track

fig. 12 is a block diagram showing another approached example, that is to say the track recorded immediately before the jump correction circuit according to the invention. or the track recorded immediately after by the same head

In connection with figs. 1 and 2, and to facilitate understanding 2A. The positions at which the pulses or hension signals of the invention, the corresponding horizontal synchronization reproduction will first be described, are recorded still image executed by a pair of diametric rotating heads on neighboring tracks Ai or on neighboring tracks Bi are trally opposite. A magnetic strip T is thus driven offset in the direction of the tracks by a distance nH or moved continuously at a standard speed in the di- + xji H, where n is a positive integer.

rection of the arrow a (fig. 2B) and a pair of rotary heads 1A 30 In the still image reproduction operation of a VTR and 2A are rotated for the alternative exploration of the helical exploration type, with the T-band of the oblique recording of the T-band in the direction of arrow b (fig. 2B). very much of fig. 2B at standstill, heads 1A and 2A explore the These heads 1A and 2A can then alternately record the same reproduction trace whose inclination and different from video signals respectively on recording tracks - that of tracks Ai and Bi , since the tape is stopped. Due to the oblique parallels Ai and Bi, making a predetermined angle of these different inclinations, the level of the video signals rebated with respect to the longitudinal direction of the T-band produced depends on the stop position of the T-band. Two In the example of fig. 2, the standard speed of the case belt are illustrated in fig. 2B. The first case is that in the-for recording is chosen so that the tracks which the two ends of an adjacent coincident-recording RI exploration trace Ai and Bi are tangent, ie substantially respectively with one end saying that there is no guard strip between the tracks, which 40 track B3 and one end of track A3. The second case is used to obtain a high recording density if the one in which the central part of track A2 covers the video signals on the T-band. In the case of recording the central part of the track exploration R2. In fig 2B, the NTSC video signals comprising 30 frames per second, the regions from which the reproduced signals are derived heads 1A and 2A diametrically opposite rotate in a manner are indicated by hatching. The conventional R2 exploration trace at a speed of 30 revolutions per second, so 45 is preferred because the level of the output signals reproduced that each head allows the recording of a frame of the signal which it delivers is high.

video. In other words, the odd frames of the signals vi- For simplification, let us assume that the rotating heads 1A

deo can be recorded on tracks Ai by the head 1A and 2A have the same direction angle. The positions of the si-

the slit of which has an angle of direction to the left with horizontal synchronization signals obtained from these ports in the transverse direction of the respective track and the headers are shown in fig. 2B, in the case where heads 1A and 2A

my pairs of video signals are recorded on the Bi tracks alternately explore the trace R1.

by the head 2A whose slit has an angle of direction towards the First, when the head 1A explores the track 3A, and right. as shown in fig. 2A synchronization signals ho-

In addition, and in a conventional manner, during the horizontal registration, from the first to the 263rd, are produced at intervals

NTSC video signals, the frames recorded on 5S the respective Th corresponding respectively to the 263 peri

each of the tracks Ai and Bi comprise 262 V2 horizontal lines or pedes. Then, head 2A explores the same track A3

horizontal periods of video information. In other words, to produce the horizontal synchronization signals 264 ms, the odd fields recorded on each of the tracks Ai to 526. By the fact that the output signals are reproduced,

contain the video signal formations of the lines or continuously, the interval between the 263rd and the 264th signal horizontal riodes (1) - (262) as well as half of the line 60 of horizontal synchronization becomes 1.25 Th, of so that it (263), while the even frames recorded on each of the occurs a jump of 0.25 Th. On the other hand, when after the ex-

tracks Bi begin with the second half of the line (263) ploration of the track by the head 2 A, the head 1A explores the same and contain in addition the lines (264) - (525). For the pre-track, there is also a jump of 0.25 Th.

miere and the second half of line 263 is recorded res- Likewise, in a reproduction mode with fixed image pectively in the odd and even frames, the two tracks 65 in which the heads 1A and 2A alternately explore the adjacent Ai and Bi are offset longitudinally at their ex-tracks A2 according to the trace of exploration R2, there also occurs a hoppers of a distance equivalent to 3/4 H, that is to say 3/4 of the jump of 0, 25 Th, as shown in fig. 2C.

distance along a track in which the horizontal lines - In the same VTR, the speed of the strip

5

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is chosen with a value equal to 2/3 of that of the standard speed, a recording model with the alignment H is formed, as illustrated in fig. 3B. It should be noted that in this case, the pitch of the tracks is actually narrower than that of FIG. 2B but that for the sake of brevity, the tracks are shown in fig. 3B with the same pitch as in fig. 2B. When one of the heads 1A or 2A sequentially explores such a recording pattern along the track RI, a reproduced signal can be derived from the hatched regions of the track A3, so that the horizontal synchronization signals are produced with the time relationships indicated in fig. 3A. In other words, the distance between the 263rd and the 264th horizontal synchronization signal becomes 1 Th and no jump is produced. The same is true, as shown in fig. 3C, in the case where heads 1A and 2A explore the track A2 of the recording along the exploration trace R2. The production of the jump of 0.25 Th in the case where no alignment H is present, with the shift (n + 0.75) H 'indicated in fig. 2B, is similar to the case in which the heads 1A and 2A are spaced apart by an angular distance different from 180 ° by an amount nH '.

Fig. 4 shows an example of a jump correction circuit capable of correcting the above jump. In fig. 4, the reference number 3 designates a delay circuit or a delay line producing a delay of 0.25 Th. The video signal reproduced by the heads 1A and 2A, then shifted in frequency, is applied to the input terminal 5. The video input signal and the output signal of the delay line 3 are supplied respectively to the input terminals 7a and 7b of a switch 6. The video signal appearing at an output terminal 7c of the switch 6 is delivered to an input terminal 9a of a switch 8 as well as to the input 9b of the same switch via a delay line 4. The video signal delivered to an output terminal 9c of switch 8 is applied to an input terminal 11a of a mode change switch 10, another input terminal 11b of which receives the input video signal. An output terminal 11c of the switch 10 is connected with an output terminal 12. A mode change signal is output from a terminal 13 to the mode change switch 10 to control the latter so that when the registered pattern of the fig. 2B in which the alignment H is not present is reproduced as a fixed image, the input terminal 1 la of the switch 10 is connected to the output terminal 1 le of this switch, whereas when the model saved with the alignment H indicated in fig. 3B is reproduced as a fixed image, the input and output terminals 1 lb and 1 le of the switch 10 are connected together. Thus, when the alignment H is present in the recording model, the jump correction is not necessary as explained above. Consequently, in such a case, the reproduced video signal is supplied as is to the output terminal 12.

In the circuit of fig. 4, a control pulse PG1, contained in the detected signal and synchronous with the phase of rotation of the head, is applied to a terminal 14. The control pulse PG 1 is then delivered to the switch 6 to control the latter and also through a frequency divider by two 15 at switch 8, also for controlling the latter. Switches 6 and 8 are therefore controlled so that when the control pulses PG 1 and PG2 are both at level "0" (lower level), the input terminals 7a and 9a of switches 6 and 8 are respectively connected to the output terminals 7c and 9c of these same switches, while when the control pulses PG1 and PG2 are both at level "1" (higher level), the other input terminals 7b and 9b of the same switches are connected respectively to output terminals 7c and 9c of the latter.

The operation of the jump correction operation, in the case where the recorded model is reproduced as a fixed image without H alignment, is explained below. If it is assumed that the time interval in which the output signal reproduced by the head 1A is designated by Tla and that the time interval in which the output signal reproduced by the head 2A is designated by T2a, these respective time intervals follow one another alternately and the video signals reproduced, including the horizontal synchronization signals indicated in fig. 5A are delivered to the input terminal 5. The period of the control pulse PG1 is that of a frame and its phase is such that it is inverted just before the first horizontal synchronization signal appearing after the end of the interval Tla or the interval T2a, as indicated in fig. 5C. The control pulse PG2, derived from the frequency divider by two 15 has a period of two fields and its phase is such that it is inverted just before the first horizontal synchronization signal appearing after the end of the interval Tla, as shown in fig. 5D.

During the first period Tla of the still image reproduction mode, the control pulses PG1 and PG2 20 are both at level "0", so that the switches 6 and 8 are in a state such that their input terminals 7a and 9a are respectively connected with their output terminals 7c and 9c, so that the input video signals are supplied directly and without change to the output terminal 12. During the next period T2a, the control pulses PG1 and PG2 go to level "1", so that the input terminals 7b and 9b of switches 6 and 8 are respectively connected to the output terminals 7c and 9c of these switches, whereby the video signal is delayed by to-30 tality of 0.75 Th by the delay lines 3 and 4 in cascade and delivered to the output terminal 12. Consequently, as indicated in fig. 5B, a delay of 1.25 Th + 0.75 Th = 2 Th is produced in the output video signal, which means that the jump is corrected.

During the period T1 a which follows the period T2a, the control pulse PG1 becomes “0” but the control pulse PG2 is always at “1”, so that the input terminal 7a of the switch 6 is connected the output terminal 7c of this switch while the switch 8 is still in the previous state, that is to say that its input terminal 9b is connected to its output terminal 9c. Thus, the video signal is delayed by 0.5 Th across delay line 4 and the jump is corrected, as shown in fig. 5B.

During the period T2a after the delay of 0.5 Th, the control pulse PG1 returns to “1” but the control pulse PG2 changes to “0”. Consequently, the input terminal 7b of the switch 6 is connected to the output terminal 7c of the latter, while the input terminal 9a of the switch 8 is connected to the output terminal 9c of the switch. Thus, s »the video signal is delayed by 0.25 Th across delay line 3 and the jump is corrected. Since the next jump of 1.25 Th can be corrected by the delay of 0.25 Th, the control pulses PG1 and PG 2 both return to "0". In this way, the jump correction operation, in a period comprising 4 frames (Tla-> T2a-> Tla-> T2a), as indicated above, is repeated cyclically.

It is possible that the jump correction circuit of fig. 4 does not produce any jump correction in the case of registration with alignment. However, when a model 60 of recording without alignment H is reproduced as a fixed image, the jump correction circuit of FIG. 4 is necessary to carry out a control operation such that the four possible combinations of the states of the two switches 6 and 8 are presented in a predetermined order, such a command being rather inconvenient to perform.

In addition, the circuit of FIG. 4 requires two delay lines 3 and 4 in cascade to delay the video signal by 0.75 Th. The presence of these two lines in cascade increases however

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the insertion weakening, which produces a milior deterioration to that of FIG. 4, a reproduced video signal is applied

the quality of the video signal. at an input terminal 5 and, between input terminals 5 and

An embodiment with a disposition of the se- output heads 12 is a circuit or a delay line 3 pro-

lon the present invention to avoid the problems resulting in a delay of 0.25 Th, a circuit or a delay line generalized above will be described below in connection with FIG. 5 4 producing a delay of 0.5Th, switches 6 and 8 and

6. In this case, a pair of head 1A and 1B are arranged with a mode change switch 10.

diametrically opposite and another head 2A is pre- In the circuit of fig. 9, the delay lines 3 and 4 are seen in a position offset with respect to the head IB of a connected in parallel on the input terminal 5 and the signals predetermined angle 0 in the corresponding direction of rotation produced by these lines are respectively delivered to (n + 0.25) Th, where n is a positive integer. The angle of di- to the input terminals 7b and 9b of switches 6 and 8. The rection of the head 2A is chosen to have the same value as that of the other input terminals 7a and 9a of switches 6 and 8 received. -

head 1 A, this angle being different from that of head 1B. In both wind the video signal reproduced from the terminal the example described, the direction angles of the heads 1A and 1B are 5 and the output terminals 7c and 9c of the switches 6 and 8 are respectively + 7 ° and - 7 °. respectively connected to the 1 lb and 1 la input terminals of the

The recording operation is performed by the pair of mode change switches 10. The head switches 1A and 1B producing two adjacent tracks offset Ion- 6 and 8 are respectively controlled by gitudinal pulses with a distance of 3 / 4 H along a track, control PG1 and PG2 so that when the pulse as shown in fig. 2B. PG1 is at level "1", terminals 7b and 7c of switch 6

During the normal reproduction operation, the two are connected together and only when the pulse PG2

adjacent tracks are reproduced respectively by the heads 20 is at level "1", the terminals 9b and 9c of the switch 8 are

1A and 1B, while one of the two adjacent tracks which has been linked together.

recorded with head 1A is reproduced by heads 1A and 2A When recording without alignment in the still image reproduction mode. In the case of H, as shown in fig. 7B, is reproduced in a mode with reproduction mode with fixed image by the heads 1A and 2A, it is fixed image, the terminals 11 a and 11 c of the change-visible switch that a jump in the horizontal synchronization signal occurs. mode 10 are connected together. A reproduced video signal, even if the recording model includes the product comprising H-horizon synchronization signals indicated in fig. 3B. It should however be noted that this pillowcase having the time relationships indicated in fig. 10A is then jump can be more easily compensated than in the case of the circuit delivered to the input terminal 5. In this reproduced video signal, cooked from FIG. 4. the distance between the two horizontal synchronization signals

The way in which the jump in the reproducing mode reproduced at the exit of the head 1A and at the exit of the still image duction head of a recording without alignment H 2A is produced is 1.5Th, as indicated previously. . The impulse of is explained in relation to fig. 7. When the head 1A ex-control PG2 has a phase such that it passes to the upper level

plore the part spanning tracks B3 and A3 in fig. 7B, a lower and lower level just before the 264th video signal signal comprising the horizontal clock synchronization signals in the interval T2a, as in-

zontale is produced with the relation of times indicated in the 35 shown in fig. 10C. Since switch 8 is controlled

upper line of fig. 7A. By the fact that the head 2A is in by the control pulse PG2 so that when a position offset with respect to the head 1 A, when this the pulse PG2 is at level "0", the terminals 9a and 9c of the how

head 2A explores the recording, synchronizer signals 8 are linked together while when the pulse

horizontal tion are produced, each of these being PG2 resolution is at level "1", terminals 9b and 9c of the switching

delayed by 0.25 Th in comparison with each of the protector signals 8 are linked together, the distance 1.5Th in the signal signal with an arrangement of the heads at 180 ° distance from the video appearing at the output terminal 12 becomes 2Th or ITh gular, as indicated in the middle line of fig. 7A. as shown in fig. 10B, which means that the jump can be

Consequently, the distance between the 263rd and 264th si- corrected.

general horizontal synchronization becomes 1.5 Th, so When recording with H alignment indicated in that a jump of 0.5 Th is produced. 45 fig. 8B is reproduced in still image mode, the terminals

On the other hand, when one passes from the position of head 2A to the 1 lb and 1 the of the mode change switch 10 are position of head 1 A, the distance between the 526th and the first connected together. In this case, a video signal reproduced as

horizontal synchronization signal becomes (1.25 - 0.25) Th taking horizontal synchronization signals having the

= ITh, so that no jump is produced. As the time relationships indicated in fig. 11A is delivered to the terminal qué, when the output signal is reproduced by the head 2A at the input 50 5. In this reproduced video signal, the distance between the locations of the head 1 A, a jump of 0.5Th is produced, but when the horizontal synchronization signals, due to the change of output signal is reproduced by the head 1A instead of the head of the output signal reproduced passing from the head 1A to the head

2A, no jump is produced. 2A is 1.25Th whereas when changing the head 2A to the

An explanation of the jump that occurs when the 1 A recorder is 0.75Th. In this case, the control pulse having the alignment H indicated in fig. 8B is 55 PG1 is produced with a phase such that it passes to the reproduced level with a fixed image along an exploration trace RI is greater just before the first synchronization signal ho-

given below. In such a case, when a horizontal output signal in the interval Tla and it passes to the lower level

is first derived from head 1A and that a laughing output signal just before the 264th horizon synchronization signal is then derived from head 2A, the distance between the 263rd and the pillowcase in the interval T2a, as shown in fig . 11 C. The

264th horizontal synchronization signal becomes 1.25Th 60 switch 6 is controlled by the PG1 pulse so that the distance between the 526th and the first synchro signal only when the latter is at level "0" terminals 7a and 7c nisation horizontal becomes 0.75 Th, as shown in fig. of this switch 6 are interconnected and that when

8A. the PG1 pulse is at level "1" terminals 7b and 7c of the

A similar jump is also produced in the case where the inverter 6 are linked together. Consequently, and as a recording, it is reproduced as a fixed image along a trace of ex- 65 indicated in FIG. IIB, in a video signal derived from the R2 plotting terminal, as shown in figs. 7B and 8B. output 12, the distances of 1.25 Th and 0.75 Th from the video signal

Fig. 9 shows an example of an input correction circuit each becoming ITh, so that the jump correction according to the present invention. With the circuit of fig. 9, if - a jump can be made.

As described above, and according to the present invention, during the still image reproduction mode of the recording without H alignment, the jump can be corrected by alternating the states in which the delay line 4 of 0.5Th is inserted and the states without this delay line, while in the still image reproduction mode of a recording with H alignment, the jump can be corrected by alternating the states in which the delay line 3 of 0.25Th is inserted and the states without this delay line. Consequently, the jump correction circuit according to the invention becomes much easier to control in comparison with that of FIG. 4 and it makes it possible to avoid the defect in the deterioration of the quality of the reproduced video signal originating from the increase in the insertion loss due to the fact that two delay lines are connected in cascade, as in the circuit of the fig. 4.

In the embodiment described above, the angular displacement is chosen to be 0.25 H but it is visible that this angular displacement can be chosen to be of general value (n + 0.25 H) where n is a positive integer.

Fig. 12 shows another embodiment of a jump correction circuit according to the invention in which the reproduced video signal is supplied to an input terminal 20 and through a buffer amplifier 21 to a frequency converter 22. The frequency converter is used to amplitude modulate the video signal with a protective signal delivered by a reference oscillator 23 and the modulated video signal of the converter 22 is delivered to a pair of delay lines 24 and 25 realizing respectively the delays of 0, 5 H and 0.25 H. The reason for this amplitude modulation of the video signal is that the latter has a relatively large bandwidth ranging from the zero frequency to a frequency of 3.58 MHz, so that it does not cannot pass through delay lines whose bandwidth is limited to the high frequency range. Consequently, by modulating the video signal with a carrier of 10.24 MHz, the components of the lower sideband of the modulated video signal can cross delay lines whose frequency band is 8 MHz ± 2 MHz.

The outputs of delay lines 24 and 25 are connected with terminals 26a and 26b of a first switch 26, the output terminal 26c of which, connected to the movable arm of the switch, is connected by an amplifier 27 to level adjusters 28 and 29, the outputs of which are connected respectively with the input terminals 30a and 30b of a second switch 30. The level adjusters 28 and 29 are used to compensate for the difference in level between the output signals of the delay lines 24 and 25 The output 30c of the switch 30 is connected with a frequency converter 31 in which the modulated video signal is demodulated to recover the primitive video signal. The frequency converter 31 receives the carrier of the oscillator 23 through a phase shifter. The circuit of the present invention comprises two phase shifters 32 and 33 of the phase of the carrier signal producing different values of the phase shift corresponding to the phase shifts in the respective delay lines 24 and 25. The outputs of the phase shifters 32 and 33 are connected to terminals 34a and

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34b of a third switch 34 which is switched in synchronism with the switching of the first switch 26.

The circuit further comprises a fourth switch 35 receiving the video signal reproduced from the amplifier 21 at an input terminal 35a and the demodulated video signal delayed at an input terminal 35b. The movable arm of the switch 35 is connected to an output terminal 35c connected to an output terminal 37 of the device by a circuit for inserting a vertical synchronization signal 36 which will be described later in detail, the switch 35 is controlled by the switching signal indicated in fig. 10C during the reproduction of the recording model of FIG. 7B and by the switching signal indicated in fig. 11C during the reproduction of the recording model of FIG. 8B.

15

The switches 26, 30 and 34 are switched in synchronism in response to a mode signal delivered by a terminal 38 so that during the reproduction of the recording of FIG. 7B, the movable arms of these switches are res-pectively connected with the terminals 26a, 30a, and 34a and that during the reproduction of the recording of FIG. 8B the movable arms are respectively connected with the terminals 26b, 30b and 34b of the same switches. The reference 40 designates a switching signal generator producing the switching signal PG1 (fig. 11C) or PG2 (fig. 10C) from a pulse signal produced in the pulse generator of the drum (not shown) and delivered to a terminal 39. It is visible that the switching signals PG 1 and are selectively delivered in response to the mode signal. Furthermore, the switching signal generator 40 receives another control signal from an alignment jump detector 41 H which detects the jump of the horizontal synchronization signal. The control signal is used to switch the delay line when the jump does not occur in synchronism with the head change signal, in the slow motion and fast playback modes.

The video signal corrected as explained above is delayed by 0.25 H or 0.5 H during each interval or second frame interval. This produces a vertical shake of the image reproduced on a television receiver. In order to avoid this problem, a vertical synchronization reference signal VD is inserted into the corrected video signal via the circuit 36. The signal VD is formed by the head switching signal which is first 45 different in a differentiation circuit 42 delivering the differentiated pulses. The latter are delayed by a predetermined quantity in a phase control circuit VD 43 to determine the position of the signal VD to be inserted. Finally, the signal VD is produced from the delayed pulse re-50 in the pulse generation circuit VD 44 and is mixed with the video signal in circuit 36.

It is clear that many modifications or variations can be made by a person skilled in the art without departing from the scope of the present invention, so that the latter should only be judged on the basis of the claims.

VS

8 sheets of drawings